Band saws usually have a frame which holds a workpiece, and include a support, holder or carriage for pulleys or sheaves over which a saw band is looped, the saw band being driven by a motor which drives at least one of the pulleys. The carriage further holds guide elements which guide the saw band into suitable orientation so that the saw band will cut into the workpiece in accordance with a desired configuration or angle. The saw band is an endless loop, passing through the workpiece and being guided therethrough by slide guides to stabilize the orientation of the band with respect to the cut to be made. The carrier or carriage may be pivoted on the table, or may be slidable with respect thereto in order to appropriately feed the saw band against the workpiece.
Band saws of this type are made in various models. The present invention is applicable to all the types of band saws. In one type of band saw, the drive and guide pulleys are located essentially horizontally opposite a horizontal workpiece holding table. The height adjustment of the saw band with respect to the workpiece can be controlled mechanically or hydraulically, so that the saw band, upon being driven by the motor, will enter into and engage the workpiece.
In accordance with another construction, the carrier or carriage for the sheaves or pulleys of the saw band are pivotably connected to the machine frame. Pivoting movement is controlled mechanically or hydraulically. Another construction utilizes a vertically positioned carriage or saw band pulley carrier which which can be moved relative to the workpiece by horizontal guide and feed structures.
Most band saws are so made that the carrier structure or carriage for the saw band pulleys also carries all other essential elements for the operation of the saw, namely the return pulley, the drive motor, and the guide element to twist the saw band, or otherwise position the saw band, so that it will cut in the proper sawing plane. Further, means to tension the saw band by mechanical, electrical, or hydraulic repositioning of the idler pulley about which the endless saw band is looped, electrical and/or pneumatic control apparatus, bearings for the respective pulleys, ducts for supply of cooling and/or cutting fluid, and the like. The carrier structure or carriage, thus, is an important element for the overall operation of the band saw, including guidance and feeding of the saw band with respect to the workpiece.
It has been customary to make the carrier element or carriage for the sheaves or pulleys as a cast-iron structure, or as a frame structure, for example a hollow beam, which is welded together. The respective surfaces necessary to provide for guidance, and detachment elements for the motor, for bearings and the like, are then constructed by machining the casting or welded construction on boring and/or milling machines, so that that the raw casting will receive the required dimensions. This requires expensive machine tools, and results in high manufacturing and machining costs.